Prof. Stephan Lautenschlager, MD, Chief of Dermatology at the Stadtspital Triemli, provides information in an interview about the epidemiology, methods of diagnosis and therapy of actinic keratosis. In addition, he goes into more detail about how dangerous this disease is and the risk of developing into a malignant spinalioma.
Prof. Lautenschlager, actinic keratosis is not yet considered a skin cancer, how dangerous is the disease?
Prof. Lautenschlager:
Today, actinic keratoses are thought to be part of a disease continuum initiated by UV exposure. The primary cause is UV-induced light damage, followed by the formation of actinic keratoses, which in turn can develop into squamous cell carcinoma. Due to the cytological changes, which are restricted to the epithelium, actinic keratoses are classified as in situ carcinomas according to the current doctrine.
What is the prevalence of actinic keratosis and which populations are most affected?
It is well known that individuals with light skin complexion tend to develop actinic keratoses in areas with high UV exposure. Thus, they are found in about 50% of adults in Australia, and in about 10-25% in our latitudes. Even higher prevalences appear to be present in those over 70 years of age. In the past, men were more frequently affected than women as a result of occupational exposure. However, this relationship has evened out over the past 10-20 years due to increases in recreational UV exposure.
What is the risk of developing malignant carcinoma (spinalioma) if you already have actinic keratosis? The numbers from research seem to vary widely here….
Actinic keratoses may persist stably for years, disappear spontaneously in some cases, or even turn into spinocellular carcinomas. Unfortunately, neither the time of transformation to invasive carcinoma nor the forms prone to it can be predicted. It is estimated that within ten years, 15-20% of lesions will progress to carcinoma.
What methods should doctors use to diagnose actinic keratosis?
Basically, the diagnosis is to be made clinically, whereby different forms may exist, which then also present themselves histologically differently, for example lichenoid, bowenoid, pigmented and atrophic to cornu cutaneum-like hypertrophic keratoses. Especially in the case of thickened – so-called infiltrated – keratoses, biopsy should exclude an invasion and thus a spinocellular carcinoma. In the hands of the skilled, an assessment with the reflected-light microscope can additionally be helpful.
Is a clear diagnostic distinction between actinic keratosis and spinalioma even possible?
Only thickening indicates a possible spinocellular carcinoma.
Thus, in cases of doubt, histologic evaluation should always be performed. In addition, it should be noted that histologically in the epidermis an actinic keratosis is indistinguishable from a spinocellular carcinoma and thus must also be biopsied sufficiently deep.
What other diseases should be given special attention in the differential diagnosis?
If rarely a single change has to be differentiated, lightly pigmented, flat seborrheic keratoses or at most viral induced changes, superficial basal cell carcinoma or Bowen’s disease have to be distinguished. Less frequently, purely inflammatory changes such as discoid lupus erythematosus must be differentiated.
There is a possibility of spontaneous regression. Are therapy measures recommended at all?
On the one hand, multiple actinic keratoses frequently exist, indicating so-called field carcinization. This multiplies the risk of transformation to spinocellular carcinoma. On the other hand, progressive lesions cannot be distinguished from regressive lesions, which is why there is consensus among experts to treat actinic keratoses. However, there is still no consensus on which therapeutic measure will achieve the best result in which situation.
What are the drug therapy options? Which one seems most effective to you?
There are numerous treatment options available. The decision must be made according to the number, localization, skin type and other individual characteristics of the patient. In addition to life situation, comorbidities, compliance, and patient preferences must also be considered. Last but not least, the experience and familiarity of the treating physicians also plays a decisive role.
A widely used and effective treatment for more isolated forms is cryotherapy. If the goal is to treat field cancerization, to treat incipient changes that are not yet visible if possible, then photodynamic therapy should be given preference, as well as local treatment with imiquimod, topical fluorouracil, or at most diclofenac in early stages. A promising new topical therapy with ingenol mebutate gel was recently approved in Switzerland. Due to the fact that the therapy is only required for a short period of time, it can be assumed that patient compliance is significantly improved. For extensive cases, especially when the whole scalp is affected in elderly patients, the possibility of treatment by X-rays must also be considered, which usually leads to a long remission period, but usually requires six cycles of treatment.
What advice should physicians give their patients in case of actinic keratosis?
In addition to education regarding the warning signs of incipient transformation to spinocellular carcinoma, patients must be accurately instructed on sun protection measures. In addition to textile sun protection, regular application of sunscreens with a high to very high sun protection factor is a top priority. Of course, solariums should also be avoided.
Interview: Andreas Grossmann
